As is well known, such textile materials, e.g. made from polyamides, acrylonitriles, acetates and triacetates, polyesters and polyvinyl chlorides, while having excellent properties in many respects, suffer from the drawbacks as compared with textile material of vegetable or animal origin, that they have a hard touch and a rather glossy appearance. Besides, they have poor heat insulating properties and will only absorb or adsorb very small quantities of moisture.
In order to remove these drawbacks, i.e. to improve the bulkiness and/or texturation of the textile material, a process has been proposed according to which the textile goods are first subjected to treatment in a strongly attacking shrinking bath containing as the active component a swelling agent, while at the same time being subjected to ultrasonic waves, and are immediately thereafter washed with a washing liquid that may contain a neutralizing agent for the active component of the shrinking liquid.
As the active component of the shrinking liquid phenol in a concentration of 3-8% in aqueous solution has up to now primarily been used for the treatment of polyamides, but many other compounds may come into consideration, depending on the type of synthetic textile material.
As a result of this known process, the filaments or fibres of the yarn are spread apart, whereby a great number of small cavities are formed between the individual filaments or fibres, which cavities will give the thread as a whole somewhat more fluffy contours, whereby the fabric becomes more voluminous and less glossy, and will also contribute towards increasing the heat insulating and moisture adsorbing or absorbing properties.
In order to obtain useful results, it has been found necessary to operate at very short and well-defined times of treatment, viz. only a fraction of one minute in the shrinking bath. If the time of treatment is increased and the concentration of the shrinking agent is made correspondingly lower, it is found that just a uniform shrinking, but no spreading of the filaments or fibres will take place.
It is a drawback of the known process that, in addition to the useful quantity of swelling agent migrating into the filaments of the yarn and causing their surface layers to swell, a relatively great quantity of swelling agent is removed from the shrinking bath with the water soaking the textile material. This additionally removed quantity of swelling agent does not only result in increased processing costs, but may also be difficult to dispose of. Thus, if in the case of polyamide textiles phenol is used as a swelling agent, a considerable quantity of phenol will go into the washing water and may be a source of considerable nuisance if the waste water is drained off to a sewage system, or to rivers or lakes.